Monday, October 4, 2010

Dispatch from Chang'E-2: Sinus Iridum

Clementine (1994) Near-Infrared Multi-Spectral Mosaic (USGS Map-A-Planet] view of Sinus Iridum (44.4°N, 330.0°E), the 414 km-wide "Bay of Rainbows" on the northwestern tier of Mare Imbrium (with the lofty Jura Mountains on its west). Xinhua news agency reports the relatively high-latitude feature is the intended target of a low a planned low-perigee, high-resolution survey by Chang'E-2 as the intended target for a planned landing by Chang'E-3 in 2013.

Dr. Yong-Chun Zheng, associate professor at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) reports from Beijing, "the high energy particle detector (HPD) on board Chang'E-2 was switched a day after Trans-Lunar Injection, "suggesting the scientific instrument has begun working"

"Data transmitted from Chang'E-2, such as the temperature, voltage and power of the HDP, are all within range, indicating the instrument works well."

Chang'E-2 carries seven scientific instruments. "The HPD is responsible for surveying the space environment in the journey from the earth to the moon and space environment near the moon," Zheng said. HPD is one of two instrument stages of the Chang'E'2 Space Environment Monitor System, designed to measure heavy ions, proton spectra and the composition and spatial distribution of low-energy solar wind.

Second of Three Course Corrections Unnecessary

Beijing Aerospace Command and Control Center completed an initial adjustment of Chang'E-2's course at 12:25, October 2 (Beijing time). Further adjustments are expected, but Xinhua has reported that the second of three planned TLC maneuvers had been deemed "unnecessary."Chang'E-2 was launched at 18:59:57 pm, October 1 (Beijing time) and was directly inserted into an earth-moon transfer orbit. Direct Earth-Moon transfers generally require an initial critical course correction. "Chang'E-2 needed to slightly change its orbit at the appropriate time," Zheng reports. "If the orbit correction is not on time, the satellite could depart from its correct orbit to the moon and might not be captured by the moon's gravity," which is overwhelmed first by Earth and then, about half the distance to the Moon, by the Sun. "So, for Chang'E-2," Zheng said, "the orbit correction was very important."Telemetry indicates the Long March 3C booster successfully sent Chang'E-2 into its target course and, "everything is going well," Zheng said. "We give the mission perfect evaluation marks.""Chang'E-2 needed to slightly change its orbit at the appropriate time," Zheng said. "If the orbit correction is not on time, the satellite could depart from its correct orbit to the moon and might not be captured by the moon's gravity," which is overwhelmed first by Earth and then, about half the distance to the Moon, by the Sun.China's state news agency Xinhua reported Monday Chang'E-2 is expected to travel a total of 112 hours before lunar orbit insertion.Xinhua also disclosed the relatively high-latitude Sinus Iridum, the familiar 411 km "half-moon" embayment "Bay of Rainbows," on the northwestern edge of Mare Imbrium is one intended target of the Chang'E-2 survey. "To acquire more detailed moon data, Chang'E-2 will enter a lower lunar orbit about 100 km above the surface (compared with the 200-km altitude of Chang'E-1) according to the control center."The satellite will eventually be maneuvered into an orbit just 15 kilometers above the moon. At that point, Chang'E-2 will take pictures of moon's Bay of Rainbows area, the proposed landing site for Chang'E-3, with a resolution of 1.5 meters. The spatial resolution of Chang'E-1's CCD stereo camera was 120 meters, said Wu Weiren, chief designer of China's lunar orbiter project.